On my mac book pro i just imported the files like you would any other files. Are you grabbing them off the camera or are they on a dvd? Dont hold me on this but i remember reading somehwere that the m2ts files would only work in FCP if you were on a machine with the Intel Core 2 Duo processor. That is how i ended up trying my mac book pro and sure enough i had success!
I was dealing with this for days! My work needed me to get files off their sony hdd camera and it was m2ts files. Of course the software that came with the camera only worked for a Pc and compressed the files alot when taking them off the camera. If you are working on an intel based mac you should be able to get the m2ts files into final cut. Other wise it wont work. I have a g5 at work and i had to use my Mac book pro to get the files into final cut. Let me know how it works out!